1. Field of the Invention
The present invention relates to an image processing apparatus and method with color correction.
2. Related Background Art
A color image recording system is known which has a host terminal for transferring record data and a color ink jet recorder for receiving record data from the host terminal and recording an image on a recording sheet by applying ink of a plurality of colors.
In this system, the host terminal uses three primary colors of RGB in order to process image data interactively with a display, and the recorder uses four-colors of CMYK because it records an image by using four color inks of CMYK.
It is necessary for this system to perform a correction/conversion process of RGB values dependent on the display into CMYK values dependent on the recorder. This conversion process for all pixels of one page data may be performed after the one page data to be printed is generated by the recorder. Recently, a system has been developed to increase the process speed, in which the conversion process is performed relative to an object on a page while one page data is generated, and the converted object is placed on this page, the object including graphics such as lines and circles, texts, and images such as scanned images.
Such a system has been assumed to use a display. Therefore, although it is possible to form an object on a page in RGB three colors, it is often impossible to form an object in CMYK four colors used by a recorder.
In such a system, the correction/conversion process of RGB into CMYK is performed in the following manner. First, RGB values of color attributes of each object dependent on the display are corrected to RGB values dependent on the recorder. The latter values are used to form the object on one page, and after one page data is generated, they are converted for all pixels into CMYK values dependent on the recorder. A process performed for each object is called a first color correction process, and a process performed for all pixels of one page is called a second color correction process.
The second color correction process converts RGB values into CMYK values. Conventionally, input RGB signals to a second color correction process unit are converted once into CMY signals by luminance/density conversion means, and a background color removal/black correction process is performed by using the minimum value of CMY as K to obtain CMYK signals.
If RGB data sets are equal, it is generally an achromatic color. Therefore, it is desired that the recorder uses only one black color. However, recording with only one black color causes an insufficient density so that in many cases, an achromatic color is often recorded by a combination of CMYK four colors. In this case, a grey balance is required to have the same color density in the range from a low density to a high density. However, a grey balance is difficult to achieve by a conventional background color removal/black correction process because this process is performed by the color conversion processing unit by using as K the minimum value of CMY signals converted by the luminance/density conversion means.
If RGB data sets are equal, it is generally an achromatic color. Therefore, it is desired that the recorder uses only one black color. However, in the above system, values once subjected to the color correction process are passed to the color conversion process. Therefore, even if the RGB values supplied to the color correction process unit are equal, it cannot be judged in practice whether the values input to the color correction process unit are equal. Accordingly, if the process of replacing the color with only one black color is performed, there is a possibility that even a chromatic color is recorded with only one black color.
The invention has been made under the above circumstances and aims at forming a black color efficiently and with high quality.
According to one aspect of the present invention, there is provided an image processing apparatus comprising: first black generating means for generating a black component from input image data of signals representative of a plurality of color components; color correcting means for correcting the colors of the signals representative of the plurality of color components and a signal representative of the black component and outputting the color corrected signals representative of the plurality of color components; and second black generating means for generating a signal representative of a black component from the color corrected signals.
The invention also aims at performing color correction in accordance with whether input image data is achromatic or chromatic.
According to another aspect of the invention, there is provided an image processing apparatus comprising: input means for inputting image data of an image; judging means for judging whether the input image data is achromatic; and color correcting means for correcting the color of the input image data and outputting color corrected image data containing a plurality of color components, wherein the color correcting means makes the levels of the plurality of color components generally equal to each other if the judging means judges that the input image data is achromatic, and makes the levels of the plurality of color components different if the judging means judges that the input image data is chromatic.